Resistor structure with adjustably positionable taps



Feb. 23, 1960 v. STEIN ET AL RESISTOR STRUCTURE WITH ADJUSTABLY POSITIONABLE TAPS Filed June 30, 1958 2 Sheets-Sheet l 1 g mum VII! S R ON W N ETR VSD N m x v m "M 6 v .I8 4 0 Z M a W, 2 W 4 .U 3

ATTORNEYS Feb. 23, 1960 RESISTOR STRUCTURE WITH ADJUSTABLY POSITIONABLE TAPS Filed June 30, 1958 v. STEIN ET AL 2,926,321

2 Sheets-Sheet 2 FIG: 3

EDWIN DREWITZ ATTORNEYS of or even less.

occasions to provide for the introduction of a large num- RESISTOR STRUCTURE WITH ADJUSTABLY POSITIONABLE TAPS Victor Stein, Fresh Meadows, and Edwin Drewitz, Flushlug, N.Y., assignors to De Jur Amsco Corporation, Long Island City, N.Y., a corporation of New York Application June 30, 1958, Serial No. 745,408

4 Claims. (Cl. 338-137) The present invention relates to a resistor structure and to the structure of a cooperating adjustable tap contact system by means of which accurate positioning of the taps with respect to the resistor is facilitated with the use of unmodified standardized equipment to produce fixed tapped resistances of small values.

In units embodying potentiometers and fixed or variable resistors, it is often desired to utilize a portion of the resistor to form a resistance of predetermined magnitude. The employment of tap contacts adapted to make electrical engagement with the resistor at appropriate points along its length is conventional for this purpose. The tap contact must be very accurately located with respect to the resistor, and to this end it has generally been necessary to design each unit for the particular application in which it is to be used. Even in the case of similar units for use under the same conditions, unavoidable variations in the resistor itself usually render it necessary that the tap contacts be individually positioned in each unit if the desired degree of accuracy is to be attained. This is, of

course, an extremely time consuming task and, moreover,

has in the past required the employment of units which must be individually modified for the particular application involved and even for the purpose of compensating .for the variations inherent in fabrication of the resistor.

The present invention has as its prime object the production of a unit including a fixed resistor with which tap ,be used with or without tap contacts, and the tap contacts may be applied thereto and adjusted thereon in such a simple manner that the necessary connections may be made in the field, and units originally purchased for use .without taps can have taps readily applied thereto even by semi-skilled personnel.

The present invention relates to improvements in the resistor structure with adjustably positionable taps disclosed in the patent to Takata #2,619,570 of November 25, 1952.

When taps are employed to produce one or more fixed resistances of small values, the tap contacts must electrically engage the resistor at very closely adjacent points.

Thus, to produce a fixed resistance of a small value, it

is desirable to design and construct the resistor and the tap contacts so as to enable such small spacing of the tap contacts as to have them embrace or extend over only a very small arc of the resistor, as for example of the order Also it is highly desirable on many ber, such as from twenty to thirty, tap contacts in a single resistor or potentiometer, and to enable the use of such a large number of tap contacts over the arc of the resistor United States Patent 0 'ice (usually 320') also requires a design of the resistor and the tap contacts such as to enable not only small but very close spacing of all the tap contacts over the arc or circumference of the resistor.

The prime object of the present invention resides in the provision of an improved resistor structure with adjustably positionable taps in which the last stated results and advantages are capable of being achieved.

To the accomplishment of the foregoing object and such other objects as may hereinafter appear the present invention relates to the structure of the resistor unit and the cooperating tap contacts, as defined in the appended claims taken together with the following specification and the accompanying drawings in which:

Fig. l is a top plan view of a potentiometer unit embodying the present invention;

Fig. 2 is a view thereof taken in cross-section in the plane of the line 22 of Fig. 1;

Fig. 3 is a fragmentary view thereof shown to an enlarged scale and taken along the arcuate line 3--3 of Fig. 1;

Fig. 4 is a perspective view of one type of tap contact member employed in the structure of the present invention; and

Fig. 5 is a perspective view of another type of tap contact member so employed.

Referring now more in detail to the drawings, and having reference first to Figs. 1 and 2 thereof, since the invention is particularly well adapted to be incorporated in a variable resistor or potentiometer structure, it is here so illustrated, such structure comprising a circular metallic casing 10 formed with a side wall 12, a bottom wall 14 and a central hub 16, the said casing carrying a rotor assembly generally designated as 18 mounted prefer- ,ably by means of the ball bearing 20 in the casing hub 16.

A resistor element 22, defined by an extended length of resistor wire 24 wound helically about a flat supporting sheet 26 of insulating material, is bent around the interior of the casing side wall 12, being separated therefrom by means of an insulating sheet 28 and separated from the bottom wall 14 by an insulating ring 30, is secured in position by means of an insulated adherent member 32 at its top. The ends 34 and 36 of the resistor are connected to externally mounted terminals such as the terminals 38 and 40, said terminals being fixed to the arcuate insulating bar 42.

The rotor assembly 18 comprises a shaft 44 to which are secured at its opposite ends the coupling members 46 and 48, well known in the art, said coupling members acting as the means for rotating the rotor assembly, the upper coupling member 46 comprising a male coupling member, and the lower coupling member comprising a female coupling member, the former being provided with a coupling pin 50 which is adapted to be received by a slot 52 formed in a spring finger 54 of an adjoining potentiometer adapted to be tandem coupled to the potentiometer illustrated in the drawings. The coupling members 46 and 48 are insulatably mounted on the shaft 44 by means of the insulator bushings 56, 56 and the insulator rings 58, 58.

The coupling member 46 of the rotor assembly carries a conductive contact arrangement including spring fingers 60 adapted to slide along the resistor 22 and a pair of spring fingers 62, 62 conductively connected to the spring fingers 60 at 64 on the coupling member 46, the spring fingers 62 being arranged to straddle and ride over a collector ring 66 insulatably mounted on the casing tub 16 by means of an insulator bushing 68, the collector ring being connected by suit-able conducting wire (not shown) to one of the terminal pins, such as the pin 7 0.

The resistor structure of potentiometer thus far described is of a conventional or standard typewell known embody therein tap members for tapping one or more fixed resistance values from the resistor element 22, said tap members and the mounting means therefor being so designed as to permit a very small spacing between the tap contacts, such for example as to have them embrace or extend over a very small arc of the resistor, as for example of the order of or even less, and so designed as to permit the introduction of a large number, such as from 20 to 30 tap contacts in a single resistor or potentiometer, it being further desirable to so construct the tap contacts and the mounting means therefor as to permit such tap' contacts to be readily adjustable over the full arc of the resistor (usually 320), and at the same time to enable the tap contacts to be readily secured in their adjusted positions.

To these ends we provide a mounting means for said tap contacts comprising spaced insulator members in the form of rings 72 and 74 secured to the bottom 14 of the resistor casing and extending substantially alongside the resistor 22 and substantially parallel to said resistor, the said ring members being fonned to provide a channel 76 therebetween and the insulator ring member 74 being formed to provide a mounting shoulder 78. And cooperating with said mounting means we provide a plurality of tap members such as the set of similar tap members 8% one of which is shown in enlarged detail in Fig. 4 of the drawings, as well as a set of tap members 82 and 84, the tap member 82 being shown in enlarged detail in Fig. 5 of the drawings.

Each tap member is provided with a tap contact C adapted to engage the resistor 22 and a mounting part M adapted to be engaged over the shoulder 78 of the insulator ring '74, the latter acting as a track over which the mounting part M is adapted to ride for slidably adjusting over any part of the arc of the resistor. The mounting part M of the tap member preferably comprises an inverted U-shaped element, as best shown in Figs. 2, 4 and '5 of the drawings adapted to be mounted astride the shoulder 73 of the mounting ring 74, the terminal branch m of the U-shaped element being fittedly lodged in the channel '7 6 as best shown in Fig. 2 of the drawings.

With this construction the lateral dimensions of the tap members may be made small such as to permit an arcuate spacing of adjoining tap members, center to center, of less than degrees of arc, this being illustrated in Fig. l of the drawings where such spacing as shown by the are 86 is about 7 With this construction moreover the fingers bearing the contacts C may also be bent towards each other so that the spacing of the tap contacts themselves may be of the order of 5 degrees of arc. Furthermore as will be particularly noted in connection with Fig. 1 of the drawings the dimensions of the tap members is such that a large number, and as many as 40 tap, members, could be mounted in a single potentiometer unit. These tap members are provided with wire leads 88 which may be connected to any external terminal including the terminals mounted on the arcuate bar 42. For adjustment each contact member may be moved uninterruptably over its mounting means and may then be secured in its desired fixed position by means of a spot or glob of adhesive 90 applied thereto over the area of the channel 76.

With this described construction the tap members may be also so designed as to enable a spacing between the tap contacts to be reduced to even less than 5 degrees of arc. Thus the tap contacts 82 and 84 are so designed that the contacts C, C thereof are spaced both axially as well as arcuately, the tap member 82 in this set of contacts being formed wih a lateral branch 92 in which the contact C is mounted. As shown both in Figs. 1 and 3 of the drawings, it will be apparent that the tap members 82 and 8'4 may be so closely spaced as to permit a spacing of the tap contacts themselves to as small as one to two degrees of arc.

By means of the described structure the resistor may be tapped at a large number of points and at very close asaasar. w

spacing to produce arcuate taps of very small dimensions. The unit without the tap contacts may be a standard potentiometer or variable resistor and may be sold as such to those customers who do not desire or need taps. The very same unit may be used without any modification where taps are required, the unit being constructed so that the taps may be applied thereto at any time and at any position. Inexpensive tap contacts may be employed, and may be mounted in proper position even by semiskilled labor. The resulting savings and initial'cost and any labor incident to adaptation to special installations are obvious.

While one embodiment of the present invention has been here disclosed, it will be apparent that variations may be made in the details thereof, all within the spirit of the invention as defined in the following claims.

We claim:

1. In a resistor structure, a circular casing, a resistor extending arcuately inside said casing, an insulating member secured to said casing and extending alongside said resistor and provided with a track section extending arcuately substantially concentrically with said resistor,

and adjustable tap members separate from the resistor structure each having a tap contact adapted to engage the resistor and a mounting part adapted to be engaged over said track section, the mounting parts of said tap members being slidably movable over said arcuate track section for adjustment of the tap contacts over said resistor, the lateral dimensions of the tap members being small such as to permit an arcuate spacing of adjoining tap members, center to center, of less than 10 degrees, of arc, and adjacent tap contacts of a pair of tap members being spaced axially in addition to arcuately, whereby the spacing of the tap contacts may be reduced to less than 5 degrees of arc.

2. In a resistor structure, a circular casing, a resistor extending arcuately inside said casing, an insulating member secured to said casing and extending alongside said resistor and provided with a track section extending arcuately substantially concentrically with said resistor, and adjustable tap members separate from the resistor structure each having a tap contact adapted to engage the resistor and a mounting part adapted to be engaged over said track section, the mounting parts of said tap members being slidably moveable over said arcuate track section for adjustment of the tap contacts over said resistor, the lateral dimensions of the tap members being small such as to permit a fractional arcuate spacing of adjoining tap members, center to center, and the mounting of a large number of such tap members in the resistor.

3. In a resistor structure, a circular casing, a resistor extending arcuately inside said casing, an insulating member secured to said casing and extending alongside said resistor and provided with a track section extending arcuately substantially concentrically with said resistor, and adjustable tap members separate from the resistor structure each having a tap contact adapted to engage the resistor and a mounting part adapted to be engaged over said track section, the mounting parts of said tap members being slidably movable over said arcuate track section for adjustment of the tap contacts over said resistor, the track section including a shoulder part and an adjacent channel part and the mounting part of the tap members comprising an inverted U-shaped element fitting over the shoulder part with the terminal branch of the U fittedly looped in said channel.

4. The resistor of claim 3 in which said track section comprises two concentric ring members spaced to provide said channel part.

References Cited in the file of this patent UNITED STATES PATENTS De Giers et al Sept. 7, 1948 

